The present invention relates to a reference voltage generation circuit, a data driver, a display device, and an electronic instrument.
A reduction in size and an increase in definition have been demanded for a display device represented by an electro-optical device such as a liquid crystal device. A liquid crystal device realizes a reduction in power consumption and is generally provided in a portable electronic instrument.
In recent years, an electroluminescent (hereinafter abbreviated as “EL”) device using an EL element has attracted attention. In particular, since an organic EL device including an EL element formed by using a thin film of an organic material is a self-emission type, a backlight becomes unnecessary, whereby a wide viewing angle is realized. Moreover, since the organic EL device has a high response speed in comparison with a liquid crystal panel, a color video display can be easily realized using a simple configuration. In the case where such a display device is provided as a display section of a portable telephone, an image display rich in color tone due to an increase in the number of grayscales is required.
A drive signal for displaying an image is generally subjected to gamma correction corresponding to display characteristics of a display device. The gamma correction is performed by using a gamma correction circuit. Taking a liquid crystal device as an example, a drive voltage corrected so as to realize an optimum pixel transmissivity can be output based on grayscale data for performing a grayscale display by using the gamma correction circuit. A data line is driven based on the drive voltage.
Grayscale characteristics (voltage-luminance characteristics) of a self-emission element such as an organic EL element differ in units of color components which form one pixel. Therefore, gamma correction must be performed in units of color components. In the case of outputting a voltage obtained by dividing a predetermined range of voltage using a resistor element as the drive voltage, gamma correction may be realized by selectively outputting the drive voltage corresponding to the grayscale data selected from among a plurality of voltages divided and corrected corresponding to the grayscale characteristics.
However, in the case where gamma correction circuits which realize such a gamma correction are provided in units of data lines of a panel including organic EL elements arranged in the shape of a matrix, the output pitch of a data line driver circuit which drives the data lines is limited. Since the interconnect pitch of the data lines must be reduced in order to increase the definition of the display image, a data line driver circuit which deals with an increase in definition cannot be provided if the gamma correction circuits are provided as described above. Moreover, since current flows through the resistor element of each gamma correction circuit, power consumption cannot be reduced (see FIGS. 1 and 6 of Japanese Patent Application Laid-open No. 2001-290457, for example).